Unlike resistors, when capacitors are connected in parallel (polarities
matching), their individual capacitive values add together acting like a
single larger capacitor. It is very important that they be of similar type and
voltage tolerance to perform as expected. Their actual physical placement with
respect to each other can be whatever your available space dictates so long as
all of the plus leads are connected together, and all of the minus leads,
making sure they do not short with one another...